The present invention generally relates to an apparatus and method for drying or otherwise treating materials that are conveyed through an enclosed treating environment. More particularly, the invention relates to an especially versatile apparatus and method that allow the operator to select among a variety of operational modes. Treated gases, such as heated air and the like, are able to be circulated through a variety of paths and combinations of movement that are designed to present different types of treatments and conditions to the material being treated. Included is an assembly that conveys a foraminous belt, and the treated gas path can be selected including downwardly through materials on the belt, upwardly therethrough and by an arrangement in which the materials being treated are subjected to fluidized bed conveyed conditions under which particulate materials are generally tumbled along the foraminous conveyed belt. By virtu of this invention, a single piece of equipment ca be easily adjusted so as to carry out a number of different treatment procedures that are needed for processing or treating a variety of different products, such as different dry cereal products.
Dryers, ovens, refrigeration units, and the like have been provided which circulate treated gases such as heated, pressurized air for intimate, treated contact with a variety of different products, including food products, as well as granulated or particulate materials, such as dry cereals, as well as numerous other non-edible and edible items. Typically, these devices are designed to perform primarily a single function, such as baking pizzas, making crackers, baking cookies, drying chemicals, or carrying out a particular stage in the manufacture of a particular type of dry cereal.
With particular reference to the dry cereal processing industry, cereal products of different types required different processing or treating steps. Most dry cereal products require multiple treatment steps, each necessitating a type of drying or treating apparatus that may not be suitable for any other type of treatment or processing step. For example, at certain stages, some dry cereal product preparations call for an apparatus that will permit alternating upflow and downflow of dry air through the cereal preparation as it is being conveyed through the apparatus. Such an approach may be needed, for example, for continuous cooked flake products that need to remain substantially stationary on the moving conveyor bed. Sometimes it is important to minimize movement of the cereal particulates while they are on the conveyed surface in order to achieve flavor and vitamin retention.
Other dry cereal products may require a puff-toasting or a blister-toasting procedure that can be carried out under relatively severe conditions in order to impart a particular property such as color and/or flavor development to the ultimately produced dry cereal product. Some cereal products are best prepared by including treatment with a so called fluidized bed apparatus which typically includes a solid conveyor and relies upon pressurized gas impingement onto the top surface of this solid conveyor in order to tumble or turn individual particles to thereby affect special treatments or to provide especially efficient treatment procedures. For example, grain grits can be subjected to special treatments to form same first into cup-shaped, thin flakes and then puff-toast them into thicker and larger flakes or to blister-toast them into blistered and wrinkled flakes under high temperature, short time fluidized bed conditions. Without this type of treatment, materials, such as grain grits, would form unsatisfactory flakes that look similar to fish scales.
Certain other cereal products cannot be suitably processed with this fluidized bed impingement type of equipment because the rather violent impingement activity will damage the granules. An example of a cereal of this type is one having a coating, such as a sugar coating, which will be removed from the product by frictional engagement with the pressurized air jets and with the solid conveyor surface upon which the air jets impinge. Other equipment is often needed to accomplish other procedures having their own respective time, temperature and product movement conditions and requirements.
Examples of equipment used heretofore in the cereal industry, as well as in other industries, in order to perform certain types of drying or other processing operations include the impingement type of systems such as those illustrated by U.S. Pat. Nos. 3,060,590 and 3,229,377, as well as by 3,262,217 which also includes the provision of a vibrating conveyor onto which impingement takes place. While these types of devices which basically operate on air impingement principles can be useful for certain types of applications, they do not provide the kind of versatility that can reduce the capital outlay and floor space needed for processing a variety of different products such as a full line of dry cereal products. Other devices that are useful but are of limited versatility, include those of the traveling screen type in which the products being processed are spread on a screen which is conveyed through a heated or otherwise conditioned environment. This type of an apparatus will not allow for the formation and use of a fluidized bed, and it is not particularly suitable for performing puffing or toasting operations or other procedures.
It has been found that, by proceeding in accordance with the present invention, it is possible to provide numerous types of treatment functions within a single piece of equipment. The equipment can proceed to provide operating conditions of the type provided by a traveling screen drying apparatus, while permitting adjustments in conditions to transform same into an apparatus that provides a fluidized bed to levitate and tumble the materials while subjecting them to desired time, flow and temperature conditions.
In summary, the present invention is an apparatus and method that incorporates a foraminous conveyor surface which can, when desired, be transformed into a fluidization surface that operates in the nature of a device that incorporates impingement of gas jets onto an imperforate surface along which the materials being treated are conveyed. In addition, means are provided for selectively varying the circulation path and movement velocity of the gaseous treatment fluid. Included in the means for varying the treatment procedures accomplished by the present invention is the use of a lower plenum beneath a foraminous conveyor belt, coupled with means for varying pressure exerted by the fluid within the lower plenum onto the foraminous conveyor.
It is a general object of the present invention to provide an improved apparatus and method for imparting treating fluid to materials passed through a treatment zone.
Another object of this invention is to provide an improved drying and treating apparatus and method that embody multioperational features within a single unit.
Another object of the present invention is to provide an improved apparatus and method for performing a variety of different drying or other treatment operations by modifying parameters of the treatment fluid.
Another object of this invention is to provide an improved apparatus and method for multioperational drying, toasting, or otherwise treating cereal materials with supplies of flowing gas.
Another object of this invention is to provide an improved apparatus and method wherein fluidized bed conditions can be provided without requiring an imperforate impingement surface.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description.